1. Field of the Invention
The present invention relates to electrochemical technology for the treatment of a liquid medium and concerns an apparatus for the electrochemical treatment of a liquid medium with the aim of obtaining a sterilising solution, disinfectant, decontaminant, bleach, antiseptic detergent or medicinal solution having, for example, an anti-bacterial or anti-viral action, and with the aim of disinfecting the liquid medium and/or purifying it from easily oxidised organic substances and impurities, heavy metals and iron. It is also possible in this way to effect changes in the pH and/or in the redox potential of the liquid medium.
The field of application of the present invention covers: public health establishments; food, chemical and other industries; disinfection and purification of water intended for drinking purposes and for use in swimming pools; liquid waste from technological establishments or drainage water.
2. Description of the Related Art
The electrochemical treatment (electrolysis) of a liquid medium is one of a number of processes widely used in practice. During the electrochemical treatment process, a continuous electrical current is passed through the liquid medium and directed at unipolar electrodes positioned in the liquid medium, to an anode having positive polarity and to a cathode having negative polarity. Under the action of the current in the liquid medium being processed, electrochemical reactions occur, as a result of which products of electrolysis are formed: anode products in the liquid medium processed anodically, and cathode products in the liquid medium processed cathodically. In order that the anodic and cathodic products do not become mixed with the reciprocal chemical reactions during the electrochemical treatment process, a semi-permeable barrier in the form of a diaphragm or a membrane is placed in the area between the electrodes. The electrochemical treatment of the liquid medium in the area between the electrodes, divided off by the diaphragm or membrane and forming the isolated anodic and cathodic chambers, is termed unipolar; in the anode chamber, the liquid medium, is subjected to anodic treatment, and in the cathode chamber the liquid medium is subjected to cathodic treatment. When the anodically treated liquid medium is mixed with the cathodically treated liquid medium, an electrochemically treated liquid medium with mixed anodic and cathodic products of electrolysis is obtained.
The prior art in the field of applied electrochemistry is an apparatus for the electrochemical treatment of a liquid medium, for example an aqueous solution of common salt (sodium chloride solution), containing a midstream electrolytic cell with unipolar electrodes of positive and negative polarity, which are connected to a source of continuous electrical current and positioned on both sides away from the semi-permeable diaphragm, which divides the cell into anode and cathode chambers with pipes attached to their nozzles for the introduction and removal of the liquid medium; a water-jet ejector chamber, in which the flow of water is mixed with concentrated salt water solution, a process which includes bringing it to the required concentration, is positioned on the feed line (see, for example, GB 2 253 860).
With the help of this device, anodic products of electrolysis are obtained in the solution of sodium chloride in the form of active chlorine, or cathodic products of electrolysis are obtained in the form of sodium hydroxide; a mildly acidic chlorine-containing anolyte which is used as a means of sterilisation or disinfection, and an alkali-containing catholyte, used as a detergent. This device does not allow electrochemically treated products of other compositions or pH to be obtained together with a stable concentration of mixed anodic and cathodic products of electrolysis; nor does it allow the electrochemical treatment of water intended for drinking purposes to be carried out by disinfecting it or by purifying it from active chlorine compounds, iron, heavy metals or easily oxidised organic substances.
Another prior art document refers to an apparatus used for the electrochemical treatment of water with the aim of disinfecting and purifying it from toxic organic and chemical substances and containing an electrochemical (electrolytic) cell with coaxially positioned cylindrical and bar-shaped unipolar electrodes (anode and cathode) which are connected to the exit terminals of the supply source and which are separated by a coaxial cylindrical semi-permeable diaphragm. This apparatus also has a feed pipeline for supplying the water being processed to an anode chamber, a midstream flow switching device with a midstream catalytic reactor for breaking down active chlorine, through which reactor the water is passed from the anode chamber of the electrochemical cell into the cathode chamber, and an exit pipeline for passing processed water from the cathode chamber to the place of collection (see, for example, GB 2 257 982).
An analysis of the principle of operation of this apparatus, and an experiment on its use as an ordinary water purifier, showed that its disinfection of slightly-mineralised drinking water with theoretically morbific or morbific bacteria, microorganisms and viruses was irregular, and that pipelines coming into contact with bacterially-contaminated water were themselves becoming contaminated. Therefore they had to be disinfected in order not to allow any additional bacterial contamination of the drinking water which was being purified. Disinfection of the unit was carried out using special chemical mediums, for example a 0.25% solution of sodium hypochlorite. In addition to that, the unit did not purify the water effectively enough from chemical compounds containing iron or heavy metals, and if constructed in the way described above it cannot be used for the electrochemical treatment of other liquid mediums for obtaining sterilising, disinfectant or detergent solutions.
The closest prior art to the present invention is an apparatus for the electrical treatment of water containing at least one midstream diaphragm electrolytic cell with cylindrical and rod-shaped unipolar electrodes, vertically coaxially positioned, which are connected to a source of continuous electrical current and positioned away from both sides of the semi-permeable cylindrical diaphragm which divides the cell into anode and cathode electrode chambers with a feed line for water being processed, and anodic and cathodic outlet lines for processed water, the anodic outlet line being connected with an expansion tank and this last being connected to a midstream catalytic reactor for breaking down active chlorine, from which the dechlorinated anodically-processed water is passed by way of the exit line to the place of collection (WO 93/20014).
This water purification apparatus does not sufficiently thoroughly, effectively or regularly disinfect or purify slightly-mineralised water intended for drinking purposes (with a general salt content of up to 1 g/l and a chloride concentration of up to 50 mg/l) from bacterial micro-organisms or toxic organic or chemical substances or compounds (heavy metals or iron); in addition, it lowers the pH and increases the redox potential of the water being processed, which is not always acceptable, for example where the initial pH is in the range of 6 to 7.
During the process of operating this apparatus for disinfecting water from theoretically morbific bacteria, it becomes necessary to disinfect the exit pipeline and other component parts of the apparatus, which is a process which must be carried out using industrially-produced chemical substances.
This at once makes operation of the apparatus more complex and increases its operating costs; however, the disinfection carried out periodically fails to guarantee a high-quality disinfection of bacterially contaminated drinking water, in so far as the process of electrochemically treating the circulating flow of water is not carried out until after the anode and cathode electrode chambers of the electrolytic cell have been filled, and as a result of the varying levels of hydraulic resistance in the feed pipelines (a throttle is positioned in the line through which water is passed to the cathode chamber) the electrode chambers are filled at different rates during initialisation; specifically, the anode chamber is filled more quickly than the cathode chamber.